The fabrication process of LED chip
1.LED chip inspection
Microscopic examination: whether the surface of the material has mechanical damage and linen pit lock hill chip size and electrode size is consistent with the process requirements electrode pattern is complete
As the LED chip after the scribe is still arranged in close spacing is very small (about 0.1mm), is not conducive to the operation of the process. The film of the bonded chip was expanded by a spreader to stretch the pitch of the LED chips to about 0.6 mm. You can also use manual expansion, but it is likely to cause the chip to fall and waste and other undesirable problems.
In the corresponding position of the LED stent silver glue or insulating glue. For GaAs, SiC conductive substrate, with the back electrode of the red, yellow, yellow and green chip, using silver glue. For sapphire insulation substrate blue, green LED chip, using insulating glue to fix the chip.
The difficulty of the process is the amount of dispensing control, in the colloid height, dispensing position has a detailed process requirements. As the silver plastic and insulating plastic in the storage and use are strict requirements, silver plastic wake material, mixing, the use of time is the process must pay attention to matters.
4.LED prepared rubber
And dispensing on the contrary, the preparation of rubber is the first with a plastic machine on the back of the silver paste on the electrode, and then the back with silver plastic LED installed on the LED bracket. The efficiency of the glue is much higher than that of the dispensing, but not all products are suitable for the preparation process.
5.LED hand thorns
Will be expanded after the LED chip (with glue or not prepared) placed in the jaw table fixture, LED bracket on the bottom of the fixture, under the microscope with a needle to the LED chip one by one to the appropriate position. There is a benefit compared to manual loading and automatic mounting, making it easy to replace different chips at any time for products that require a variety of chips.
6.LED automatic loading
Automatic loading is actually a combination of glue (dispensing) and the installation of the chip two steps, first in the LED bracket on the silver glue (insulation), and then use a vacuum nozzle to suck the LED chip moving position, and then placed in the Corresponding to the stent position. Automatic loading in the process mainly to be familiar with the equipment operation and programming, while the equipment of the glue and installation accuracy to adjust. In the choice of the nozzle on the choice of bakelite nozzle, to prevent damage to the surface of the LED chip, especially blue, green chip must be bakelite. Because the steel mouth will scratch the chip surface current diffusion layer.
The purpose of sintering is to soften the silver paste, sintering requirements to monitor the temperature to prevent the poor batch. Silver sintering temperature is generally controlled at 150 ℃, sintering time of 2 hours. According to the actual situation can be adjusted to 170 ℃, 1 hour. Insulating rubber is generally 150 ℃, 1 hour.
Silver plastic sintering oven must be in accordance with the process requirements of 2 hours (or 1 hour) to open the replacement of sintered products, the middle shall not be free to open. Sintering oven can not be used for other purposes to prevent contamination.
8.LED pressure welding
The purpose of welding is to lead the electrode to the LED chip to complete the product inside and outside the lead connection work.
LED welding process is gold wire and aluminum wire welding two. Aluminum wire welding process for the first LED chip electrode on the pressure on the first point, then pull the aluminum wire to the appropriate bracket above, press the second point after the break aluminum wire. The gold bullion process burns the ball before the first point of pressure, and the rest is similar.
Pressure welding is the key link in LED packaging technology, the main need to monitor the process is the pressure welding wire (aluminum wire) arch wire shape, solder joint shape, tension.
LED packaging is mainly a little plastic, potting, molding three. Basically, the difficulty of process control is the bubble, more than material, black spots. Design is mainly on the selection of materials, use a combination of good epoxy and stent. (The general LED can not pass the air tightness test)
LED Dispensing TOP-LED and Side-LED for dispensing. Manual dispensing package on the operating level is very high (especially white LED), the main difficulty is the amount of dispensing control, because the use of epoxy in the process will become thicker. White LED dispensing there is also the phenomenon of phosphor powder precipitation caused by the color difference.
LED encapsulation package Lamp-LED package in the form of potting. Potting process is the first injection molding cavity in the LED injection of liquid epoxy, and then insert the welding of a good LED bracket, into the oven to epoxy curing, the LED from the mold out of the shape.
LED molded package will be welded to a good LED stent into the mold, the upper and lower mold with a hydraulic press mold and vacuum, the solid epoxy into the injection of the entrance of the hydraulic pressure into the mold with the hydraulic plunger, The epoxy enters the LED forming tank and solidifies it along the glue path.
10.LED curing and post cure
Curing is the encapsulation of epoxy curing, generally epoxy curing conditions at 135 ° C for 1 hour. The molded package is typically at 150 ° C for 4 minutes. After curing is to make the epoxy fully cured, while the thermal aging of the LED. Post-curing is important for improving the bonding strength between epoxy and stent (PCB). The general conditions are 120 ° C for 4 hours.
11.LED cut and scribble
As the LED is connected together in the production (not a single), Lamp package LED cut with the use of cutting ribs LED brackets. SMD-LED is in a PCB board, the need for dicing machine to complete the separation work.
Test the LED optical parameters, test the size, at the same time according to customer requirements for LED product sorting.